Servomotor system for aircraft



.July 11, 1939. B. c. CARLSON SERVOMOTOR SYSTEM FOR AIRCRAFT Fiied March'20, 1936 3 Sheets-Sheet 1 July 1, 1939.

B. G. CARLSON SERVOMOTOR SYSTEM FOR AIRCRAFT F'il ed March 20, 1936 :sSheets-Sheet 2 I V I Y 5 ENVENTOR gkrfi. GHRLSON B. G. CARLSONsERvoMoTbR SYSTEM FOR AIRCRAFT July 11, 1939.

3 Sheets-Sheet 3 Filed March 20, 1936 'INVENTOR B5777? C0 LSO HlsATTORNEY.

Patented July 11, 1939 UNITED STATES 2,165,451 'SERVOMOTOR. SYSTEM FOR.AIRCRAFT Bert G. Carlson, Bellerose, N. Y assignor to Sperry GyroscopeCompany, 1110., Brooklyn, N. Y., a. corporation of New York ApplicationMarch 20, 1936, Serial No. 69,757 7 4 Claims.

trol surfaces. In very large aircraft, the pull required to move thecontrol surfaces becomes more than can be readily handled by man powerand it becomes of importance to supply a power actuated servo system tooperate the control sur faces. The automatic pilot for aircraft may befitted readily into such a servo system, either by operating the largeservo motors directly from the control unit of'the automatic pilot orindirectly from the standard servo motors supplied with the pilot.

Referring to the drawings, disclosing several forms my invention mayassume,

.Fig. 1 is a diagrammatic view of the servo motor system; with astandard automatic pilot coupled into the same.

Fig. lA is a sectional detail of one of the pneumatically operatedcontrol valves of the control unit of the automatic pilot.

Fig. 2 is a transverse section, on a larger scale, of one of the heavyduty servo motors.

Fig. 3 is a section taken approximately on broken line.33 of Fig. 2.

Fig. 4 is a section taken approximately on broken line 4-4 ofFig. 3.

Fig. 5 is a partial section of amodifled form of servo motor for use inthe form of the invention shown in Fig.

Fig. 6 is a diagrammatic view of a modified form of the invention, inwhich only one system of servo motors is employed.

automatic p'ilot servo motors used in Fig. 1.

Fig. 8 is a detail of Fig. 5.

In the plane diagrammatically shown in Fig. 1, the control surfaces areof a large size, requiring a greater force to move than can be exertedbya pilot. Since the automatic or gyro pilot is also designed for-exerting a force on the order of that exerted by the human pilot, Ifind it desirable toemploy additional high thrust servo motors foroperating the rudders, which may be .controlled either from the manualcontrols or the standard automatic pilot servo motor syste'm. As shown,a separate hydraulic cylinder l, 2, 3 is employed for each ofthe controlsurfaces, 1, e., the rudder R, the elevators E a d ailerons A.. pistonrods 4 and 4 at each endand also sli e valve rods 5 and 5' at each endEach slide val e rod and piston rod is connected to the same 55 cables5, '5' leading to.the control surface through Fig. 7 is a verticalsection through one of the a Each motor i's'shown as havi g' individualcables I and 8', -('l, l) the former connected to the piston rod 4 andthe latter to the slide valve rod 5. Cable 8 is shown as passing. arounda pulley 9 on theslide valve rod and thence to the steering pedals Hi,It, whence it passes back to the piston rod II on the gyro pilot servomotor I2. The other end H of said rod is connected to the cable 8 andback around pulley 9' on the-piston rod 4'. Hence the slide valve 5, 5'and the main servo motor may be moved either from the standard manualsteering control means I l0 or from the gyro pilot servo motor l2. Whenthe human pilot is steering, the movement of his controls is exactly thesame as if he were moving the control surfaces without the assistance ofthehydraulic servo motors, since resistance may be imposed to themovement of the slide rods 5, equivalent to the ordinary resistance of acontrol surface on a small plane; Also afoliow back is provided so thatthe movement of the surface is at all times proportional to the movementof the control handle. In Fig. 1, the control unit 48 of the gyro pilotis shown as connected to servo motors l2, I2 and I!" through three pairsof pipes represented in general by dotted lines 49, one pair of pipesbeing marked 52 and 52', and the follow-up connections from the servomotor to the control unit are-shown by wires 50. Three identical controlvalves are in the control unit, one of which is shown in Fig. 1-A. Thisvalve is of light construction and is shown ascomprising a piston valve5l'having a valve stem 51 connected to. a diaphragm 68 differentiallyoperated from the air pick-off system on the gyroscope (not shown). vports so that upon movement in one direction, oil pressure is suppliedthrough pipe 69 to pipe 52 and the return effected through pipe 52 andback to the.sump through pipe Ill, and upon movement in the otherdirection the converse Said valve is provided with suitable takes place,the oil being returned through pipes H and Ill to the sump.

Thepreferred construction of the servo motor unitis shown in Figs. 2, 3and 4. In these figures, the main piston is shown -.at ii, the cylinderhaving end ports at-each end at l5, entering a channel It. In saidchannel is placed a bypass valve operable from any suitable hand means,such as'a pulley l8 operated together with the,

bypass valves of the other cylinders 2, 3 from common handle and wires18', so'that all the servo motors may be rendered inoperativesimultaneously. if desired, and the controls moved by main strength.Said passage i8 is shown as connected to the slide valve cylinder I9through "passages and 29' on each side of the bypass valve II. The slidevalve proper, 2|, is normally centralized by means of compressionsprings 22, which surround the stems 5 and 5' and hear at the outer endsagainst fixed abutments 23, and at the inner ends against a loose collar24 which bears against the enlarged ends of the valve 2| and also, inthe centralized position, against collar 25 formed by the reduced sizeof the cylinder of the slide valve as compared to the housing chamber 26for the spring.

Oil from pump 21 (Fig. 6) is supplied through the pipe 28 to a channel19 (Fig. 4) which lies parallel to a corresponding channel 30 connectedwith the exhaust pipe 3!. Oil entering channel 29 passes through one orthe other of ports 32, 32, shown in dotted lines in Fig. 3, and into oneside or the other of the slide valve 2| when the same is moved to theright or left in Fig. 3, the

' oil then passing through one of passages 20 or 20 to one or the otherside of piston is to move the same in the proper direction to turn thecontrol surface. for the oil is provided by the uncovering of thecentral port 33 which connects the other pipe 29 or 20 thereto, toreturn the oil into the channel 39 and pipe 3! to the sump 35 (Fig. 6).

It will be understood that each of the other.-

servo units may be similarly constructed and similarly connected to itscontrol surface and to the manual control stick 35 and wheel 39.

'Ihe gyro pilot servo motors may be construct-v ed as shown in Fig. 7,and as more completely described in my prior application for Safetydevice for airplane automatic pilot, now Patent No. 2,069,214, datedFebruary 2, 1937. According to this construction, a common bypass valverod 31 is provided for all three servo cylinders l2, l2 and I2", whichmay be operated from the single handle 38 so that when this handle isthrown. the wires 8, 9', etc., may all be moved by hand to control themain servo motors l, 2 and 3. Servo motors l2, l2 and I2" are also eachpreferably provided with a safety valve, whereby the motors may beover-controlled by hand even though the valve 37 not be in the bypassposition. As explained more fully inmy aforesaidapplication,

this safety valve is shown as a piston 90 normally I held against itsseat by a stiff spring M. A central channel M is provir; ed at the rightof the piston and is separated from an annular channel 93 by a sleeve M.The inner channel is in communication, through port 45, with the righthand side of a longitudinal channel 46 which is separated from the lefthand side by the bypass 31, while the left hand side 46' is connectedthrough port 41 with the annular channel 43. The piston normally closesthe end of the sleeve so that there is no communication betweenthetwoed, in this instance, to the respective servo mo- 1 tors throughpairs of pipes 52. 52', 53, 53' and 5d, 54., but only one motor .1 isshown in this Instance. The servo motor may be, of similar At the sametime a return passage construction to that shown in Fig. 2, except thatthe slide valve Zl' in this instance is arranged 'for automatic controlfrom the valve 5| on the automatic pilot 48'. Expressed diflerently, theservo motor of the pilot is built into the control valve of the heavyduty motor. The valve 5l operates to direct oil through one of pipes 52or 52 to operate the slide valve 2| which, in turn, controls the oilflow to the main piston 13'. For the preferred construction of valve 5|,reference is had to Fig. 9 of the prior patent of applicant, Elmer A.Sperry, Jr., and Mortimer F. Bates, No. 1,992,970, dated March 5, 1935,for Hydropneumatic automatic pilot, but the elements of one such valvemay be the same as in Fig. 1A.

The oil from pipe 52, for instance, enters the chamber 26' to one sideof the valve chamber l9. In said chamber is a piston 55 secured to avalve stem 56 normally pressed outwardly by a compression spring 51which bears at its inner end against a washer 58. Pipe 52 enters betweensaid piston and washer so that when oil pressure is suppliedtherethrough greater than the tension of the opposing spring (not shown)on the opposite side of the valve 2|, the slide valve will be moved tothe left in Fig. 5. Similarly, movement to the right will occur when thepressure inwthe pipe 52" is'superior. Collar 58 is preferably made inthe form shown in Fig. 8, the

' body 58' thereof being of no greater diameter than the adjacent end ofvalve 2| and'the projections bearing against collar 25,- so that theeffective area exposed to the oil is greater on the piston side than onthe valve side. In order to aid in the prompt centralization of thevalve 2| whenlthe balanced oil valve 5| centralizes, it is found that aleak should be provided to permit a slow escape of oil from the pressurechamber behind one of pistons 55. This may be conveniently effected byvery slightly opening the bypass valve 66 connecting pipes 52-and 52' orseparate leaks to the sump 34 may be provided.

Obviously, valve 2! may alsobe operated by hand through wires 8, B, asin the other form of the invention, to operate to control surface Rthrough the servo motor. In such case, the bypass valve 66 is opened.

In Fig. 6 the wires leading to the manual control handles are again at 9and I and the other wires are similarly numbered to Fig. 1. Also in Fig.6, the air pump for the gyrocontrol is shown at 60, the distributing andreducing valve atBl, and the oil reducing valve at 62.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it

for moving said valve, said means being operated" from the liquidcontrolled by said relay valve. and manually operated means foroperating said slide valve directly.

2. In an automatic pilot for large aircraft, a light duty pneumaticallycontrolled automatic pilot including a hydraulic servo motor, a directhand control, a heavy duty hydraulic servo motor for operating a control'surfaceof said craft and having a' control valve, and connectionsbetween said first named motor and said valve, and between the handcontrol and said valve, and between the hand control and said surface toope ate the said surface from either said first servo motor or by handthrough the heavy duty servo motor/or to operate said surface directlyby hand.-

3. In an automatic pilot for aircraft, .a standarcVof position, acontrol surface, a light duty p umatic-hydraulic relay valve operated byid standard of position, a heavy duty hydi'aulie servo motor foroperating said surface, a con- /trol valve therefor, means for movingthe same ing said surface, a control valve therefor, having piston meansfor moving the same operated from said relay valve, hand means formoving said is trol surface directly and means connecting said \handmeans and said heavy duty valve whereby saiti heavy duty servo motornormally assists said hand means in moving said control 15v surface.

QBERT G. CARLBON.

operated from said that named valve, and hand

